Clock initiated defroster control for mechanical refrigerators



Aplll 5, 1954 E. c. RANEY ETAL 2,674,665

cLocx INITIATED DEFRosTER CONTROL FOR MECHANICAL REFRIGERATORS FiledJune 14, 1951 2 sheets-sheet 1 Ze-STEL C PAA/Y MX Y 7 ,4 T TOR/Vf YsRANEY ET AL CLOCK INITIATED DEFROSTER CONTROL April 6, 1954 FORMECHANICAL REFRIGERATORS 2 Sheets-Shes*l 2 Filed June 14, 1951'IIlIIIIII/IIIIIIIIIIII IIIIIIIIIIIIL "IIIIIIIIIIIIIIIIIIIIIIIlIIHIIII nH u INVENTORS [J7-L C' PA/wsy BYJo/f/v L /E RMA/vw o, ATmR/vf Y@Patented Apr. 6, 1954 CLOCK INITIATED DEFROSTER CONTROL FOR MECHANICALREFRIGERATORS Estel C. Raney, Delaware, and John Liebermann,

Columbus, Ohio, assignors to Ranco Inc., Columbus, Ohio, a corporationof Ohio Application June14, 1951, Serial No. 231,464

4 Claims. 1

The present invention relates tov a control mechanism for refrigerators,and more particularly to a control mechanism to cause periodicaldefrosting of the evaporator of a mechanical refrigerator.

Another object of the present invention is to provide a controlmechanism for a mechanical refrigerator, which mechanism is-operative toinitiate defrosting cycles. in the evaporator of the refrigerator Vatpredetermined times and to terminate such defrost cycles when thetemperature of the evaporator reaches a predetermined temperature abovethe melting point of frost.

A more specific object of the invention. is to provide a controlmechanism of the character referred to having a motor-driven timemechanismwhich includesl a normally relatively slowly driven actuatorfor moving a reciprocable control member from a normal control positiontol a` defrosting control position at a predetermined time and whichactuator-.is moved. quickly beyond the range of contact with thecontrolmember following actuation of the control member thereby so that thecontrol. member may be returned to its normal position within a briefperiod without interference with the actuator.

Another object of the invention is to provide a control mechanism of thecharacter described having a member movableY in response to thetemperature of theevaporator of the refrigerator to move the controlmember t its normal position to terminate the defrosting cycles, andwhich mechanism rincludes yielding means between the motor drivencontrol member actuator and the control member so that the actuatorcannot be stalled by the control member in the event the control memberis held in its normal position by the temperature responsive member.

Other. objects. and advantages of the invention will be apparent fromthe following description of preferred. formsof embodiments oftheinvention, reference being had to the. accompanyingdrawings wherein;

Fig. 1 is a plan view of an automaticdefrost control for an electricalrefrigerator embodying the invention, certain parts being shown brokenaway;

Fig. 2 is a sectional view taken substantially along line 2--2 "of` Fig.1

Figs. 3, 4 and 5 are fragmentary sectional views taken substantiallyonline 3"-3 of Fig. 1, show.- ing certain parts of the control mechanismin different positions;

Fig. 6 is a schematicshowing of an electrical refrigerator motor andevaporatorheater cir- (Cl. 20G-38) cuits, and a switching device of thedefroster control connected therein; and

Fig. '7 is a view similar to Fig. 6, but showing the defroster controlswitch in a dierent position.

Referring to the drawings, a control mechanism It embodying theinvention is shown which is operative to initiate and terminatedefrosting cycles in the evaporator of an electrical motordrivenrefrigerating apparatus R. The refrigerating apparatus comprises acompressor and motor unit M, a condenser C and an evaporator E, allconnected to form the well known compressor-condenser expansionrefrigerating system. The power for the motor is supplied through linesLI, L2 and the operation of the compressor motor is controlled by athermostatically operated switch T which may be of any conventionalconstruction and is preferably responsive to the temperature of theevaporator. An electrical heating element H is arranged to heat theevaporator E and melt the frost therefrom when the heater is energized.Thecontrol mechanism I0 is operative to open the circuit for the motor Mand close the heater circuit to defrost the evaporator at apredetermined hour -of each day, and to open the heater circuit andreclose the motor circuit to restore normal refrigeration when thetemperature of the evaporator has reached a predetermined maximum. It isto be understood that the invention could be used in connection withmechanical refrigerating systems other than that disclosed and thatother means for applying heat to the evaporator to defrost the samecould be employed.

The control mechanism I0 includes a housing Il having a snap switch I 2supported inA one end thereof. Any suitable switching mechanism could beused and in the form shown the switch comprises a base I3 formed of asuitable dielectric material having terminal memberslll,l I5,

'I6 attached thereto and projecting therethrough to the exterior of thehousing.` The terminal member I4 is part of a bridge-like bracket I 4'which carries a fixed Contact Il on the interi-or of the housing andspaced from the base It. The terminal member I5 is part of a bar whichis attached to base I3 and carries a contact I8 which is spaced from andopposite the contact I'I. A double `contact I9 is carried on one end ofa pivoted contact strip 2t which end is snap moved between the contactsI l, It to alternatelyV engage contact I9 with the latter contacts.Y Theopposite end of the contact strip 2i) is attached toa bracket 2lofvwhich the terminal lisa 3 part and the contact strip is formed ofconducting material so that a circuit may be established from theterminal I6 through the contact strip to either terminal I4 or I5.

lhe strip 25J is snap moved in opposite directions by a toggle member 22which is disposed in a central opening in the strip and has one endpivoted to the strip and the opposite end of the toggle member hasspaced stops which engage opposite surfaces ci a stop lug 2 la to limitthe swinging movement of the toggle. A tension spring 23 is connected atone end to the swinging end or the toggle and the opposite end isattached to a tongue 24 which extends from a leg 25 of an l.. -shapedoperating lever 25 which is pivoted to shoulders 21 on the bracket 2|.The tongue 24 is adapted to extend through the opening in the contactstrip, and when the lever 2B is oscillated the spring 23 is shifted sothat its line of tension moves from one side to the other of a deadcenter line, extending through the pivot of the toggle member and theaxis of the spring, and the toggle member is thereby snapped from one ofits stops to the other and urges the contact strip in one direction orthe other between contacts il, i3 as the case may be. The leg 25 oflever 25 includes an extension 28, preferably formed of dielectricmaterial which strikes the bracket lll to limit clockwise movement ofthe lever 25.

The particular' switch construction shown is the subject of the UnitedStates patent of Estel C. Raney, No. 2,551,590, and as mentionedpreviously this particular construction is not essential to theinvention.

The pivot for the operating lever 25 is located relative to the togglemember 22 so that the tension of the spring 23 tends to rotate the leverclockwise when the axis of the spring moves to the upper side of thecenter of contact strip 20, as seen in Fig. 6, and urges the levercounterclockwise when the center tension is on the lower side of thecontact strip, as seen in Fig. '1. By this arrangement the operatinglever 26 is urged by the spring 23 to either of two extreme positions,which may be referred to as control positions, and by initially movingthe lever a predetermined distance from either control position towardthe other, the spring 23 becomes effective to urge the lever to theother position.

rEhe switch mechanism is connected in the circuit of the refrigeratingapparatus so that when the operating lever 26 is in the position shownin Fig. 6 the circuit for the motor M is established from LI through theswitch T, motor M, contacts l1, I9, contact strip 20, terminal I6 to L2,and when the operating lever is moved counterclockwise to the positionshown in 7, the motor circuit is interrupted at the contacts I1, I9 anda circuit through the evaporator heater H is established. from line Llthrough heater H, contacts i8, lil, contact strip 20, terminal I6 toline L2.

The operating lever 25 is moved from the position shown in Fig. 6, whichmay be considered its normal position, to the defrost cycle initiatingposition shown in Fig. '1 by a clock or time device 32, and is movedfrom the defrost position to its normal position by a thermoresponsivemechanism 33 which is responsive to temperature in the evaporator toterminate the defrost cycle and restore normal refrigerating cycles.

The time mechanism 32 preferably comprises an electric synchronous motor35 which drives an eccentric through a suitable reduction gear trainwhich drives the eccentric at one revolution per hour. A pawl 31 isattached to the eccentric and is oscillated thereby to drive a ratchetwheel 38 mounted on a shaft 45 which is journalled in a bushing 42 in awall of the housing H. The ratchet wheel 33 preferably has twenty-fourteeth, and the pawl 31 advances the wheel one tooth per hour so that thewheel makes one revolution each twenty-four hours. The pawl 31 has aslot 43 therein into which the wheel 38 projects, and a spring 45 urgesthe pawl into engagement with the ratchet teeth of the wheel. By thisconstruction, the walls of the slot 43 cooperate with the sides of theratchet Wheel to guide the pawl in its reciprocation. The ratchet wheelhas sufficient resistance to rotation thereof to prevent movement of thepawl along the inclines of the ratchet from rotating the wheelcounterclockwise, as viewed in Fig. 2.

In the preferred form the ratchet Wheel 33 is frictionally connected tothe rod 4l) so that the rod may be rotated manually counter to thedirection of rotation of the ratchet, and a friction clutch is providedwhich comprises a flange 45 formed integral with the rod 46 and a huband flange 43 formed integral with the ratchet wheel 38, and the flanges46 and 43 face one another and have a washer 49 of suitable frictionmaterial therebetween. The flange 48 is urged against the washer by acoil spring 5| which surrounds a portion of the rod and is compressedbetween the ratchet wheel 33 and a disk 54 on the rod.

As actuator is carried on the shaft 40 so that it may rotate freelyrelative to the shaft, and the actuator comprises a disk-shaped member56 having an arm 51 projecting radially therefrom. The arm 51 isarranged to engage and depress a leaf spring 58 attached to the leg 60of the operating lever 25 to move the lever to initiate a defrostingcycle as the disk 55 rotates on the shaft. It is desirable that themovement of the disk 55 through that segment of its rotation in whichthe arm 51 engages the spring 53 of the lever 25 be greatly acceleratedover the speed of rotation of the shaft so that the switch actuatinglever can be restored to its normal position within a relatively shortperiod Without interference with the arm 51. To provide for theaccelerated movement of the actuator disk 56, the disk is rotated by thedriving member or disk 54 which is attached to and rotates with theshaft 4D and is connected with the actuator by a torsion spring 62 and alost motion connection. The lost motion `connection is eiected by twoaxially projecting stops 63, 64 located adjacent the periphery of thedriving disk 54 and which are located at 180 with respect to oneanother. The stops 63, 64 are arranged to engage opposite sidesrespectively of the arm 51. The torsion spring 52 is coiled around therod 40 and one end thereof is hooked to the stop 64 and the other end ishooked to arm 51 and tends to urge the actuator disk 56 in the directionof rotation of the rod 4l] by the ratchet wheel 38 and urges the arm 51to the stop 64, as shown in Fig, 5.

The actuator disk 56 is restrained from rotation by the torsion springas the arm 51 thereof approaches the spring 53 by a restraining meanscomprising a detent spring 61 attached at one end to a wall of thehousing Il and having the other end yieldingly disposed in the path ofthe arm 51. When arm 51 engages the detent 61 as age'zgees shown inFigf.- 3 its` rotation is arrestedfuntili'stop (i3V engages and drivesit to deflect the-detentto release the arm. Thestoppage of rotationofthe actuator disk 56 by engagement. ofthe arm 51 withthe detent causesthe tension ofthe. torsion spring 62 to ybuild up as the disk- 551 isrotated and When'the arm 51 is positively moved by the disll54 toactuate the detent-to release the-arm, the torsion spring snap Ymovesther arm Yto stop 54 andv during the snap movement arm 51 engages thespring 58 and deflectsV the operating lever 26, as seen in Fig. 4. Thevstop 54' is located relative to stop 63 to assu-re sufficient movement`of` the arm 51 that it Will pass from the range of engagement with thespring 58 so that the operating lever can be returned "to itsnormalposition within a much shorter period. than. -would be required for therod 40 to rotate through the angle in which arm- 51 is effective tomovey the operating lever to the. defrost position.

In the form shown, stop` 64 is 180 from. stop 53, but this angle couldbe more orless'provided the angle through which arm 51 issnapped issuflicient to clear the spring 58 .of the operating lever as` described.

When the control lever 25 is moved by thearm 5i to initiate defrostingit engages a lever 10 which is pivoted on a pin 1i supportedin the Walis.of the` housing Il. The. lever 1li is preferably formed of sheet metalandthe end opposite the pivotedend has an upturned lip which is engaged`by the` leg 60 of the operating lever. Preferably the leg 55 is formedof insulating material to prevent short-circuiting through the lever-15.

The lever 'Itis a part ofthe thermoresponsive mechanism 33 and it ismovableV clockwise by an expansible Wafer 124 to return the lever 261:0yits normal position when the temperature. of: the evaporator `hasreached a predetermined vdegree above the melting point of frost.` Thewafer 12. is attached to a plate 13 which is supported in an opening'vin the housing- Il and it has a button 14 which engages a turned edgeportion 15 of the lever 1l). The Wafer has a tube 11 connected therewithand the tube has a bulb 18 at its outer end. which is suitablyv securedin heat exchange relationwith theevaporatorE. The Wafer, tube and bulb;are lled .with a vapor, such as methyl chloride or sulphur dioxide,r andthe vapor vpressure varies according to the temperature of the bulb, asis Well understood in the art. Accordingly, as the temperature of theevaporator and bulb increases the vapor pressure increases and the waferurges the lever clockwise to move the operating lever 26 toward itsnormal position. Clockwise movement of the lever 10 is limited by a stop80 struck inwardly from a wall of the housing Il.

The movement of the lever by the Wafer 12 is opposed by a tension spring3|, one end of which is hooked to a lug 82 on the lever 10 and the otherend of which is attached to a nut 83 threaded on a bolt 84 rotatablysupported in a bearing in a Wall of the housing H.

Preferably, the head of the bolt 84 is slotted so that the bolt may berotated by a screwdriver to move the nut 83 therealong and therebychange the tension of the spring. The tension of the spring governs thetemperature at Which the lever 10 is moved by the wafer 12 to cause theoperating lever 26 to be returned to its normal position, and ordinarilythe spring 8| is adjusted so that the operating lever is returned to itsevaporator andy bulb: isatleast several degrees above the-melting pointof frost;`

It is tor be noted that spring 58,` normally yieldingly moves theoperating lever 26 when it is defiected by the arm 51 as described,`butin theevent lever `1l) is in a position toblock movermentof theoperatingzlever to initiatedefrosting, springd58 yields to the arm 51sothatthelatter passes ontoy the stop. 64,. although the operatingleverhas notzmovedto cause defrosting..l This situation may occur whenthe. temperature-V of the evaporator is relatively high.. due to`loading of the refrigerator with warmr articles, or by prolongedorfrequent: opening of the; refrigerator cabinet door. The spring 58thus eliminatesthe possibility. of' thearm 51v becoming stalled,` in thesituation vjust mentionedg. and causing distortionor damage; to partsorstallingof the synchronous. motor;

It is desirable toprovide for, theselection of the hour of day at whichthe defrost'cyclesv will occur, andA this selection may bemade by,setting the driving disk 51.at a predetermined angular position byrotatingthe rod 40; Af knob 85fis `drivingly connectedto. the outerendof theirod 4l! bya key 81 attached to the rod, and the knob preferablyhas a pointer thereon (not shown) Whichregisters with a dial (not shown)on the face. ofthe housing. The dial preferably; has

vtwenty-four'markers indicating the hours ofv the day, and assuming thatthe knob ismounted on the rod so thatthe defrosting cyclesv areinitiated whenthe pointer is at the 2:0()V a. m. marking, theknob can'be rotated accordinglyyto cause de.- frosting to occur at any otherdesired hour. The clutch mechanism comprisingpflanges t6. A18 and Washer49 permits the rod. Mito be rotated by the knob in either direction,althoughfthe ratchet wheel is prevented by thev pawl from rotation in,one direction.

Alternatively, the friction clutch between the rod 4D ,and ratchet Wheelllcouldbe omitted and the rod could rthen be turned, only inthedirection of rotation of the ratchetwheel to change theidefrost hour.

By our invention We have provided a relatively inexpensivev andreliablecontrol mechanism for automatically initiating andterrninatingdefrosting cycles.v in mechanical refrigerators.` The mecha-nismis.particularly suitable for use in refrigerators having means foraccelerating the application of heat to the evaporator to melt collectedice or frost therefrom since the clock operated member for initiatingthe defrosting cycle is quickly removed from its actuated positionfollowing the initial operation of the control mechanism. Furthermore,in the event the evaporator is too warm for effecting the defrostingoperation, the time mechanism cannot be stalled by the inability of thecontrol lever to move to its defrosting position.

While the preferred form of the invention has been shown, it is to beunderstood that other forms and adaptations of the invention may be madewithout departing from the spirit of the invention as defined in theclaims which follow.

Having thus described our invention, We claim:

1. A control mechanism comprising a control member movable between twocontrol positions, means for moving said member from one of saidpositions to the other, an actuator movable in a path in Which it movesinto and out of range of operative engagement with said control memberto move said member from said other position normal position when thetemperature in the toward the rst mentioned position, power meanslincluding a driving member having a lost motion driving connection withsaid actuator permitting movement of said actuator independently of saiddriving member through said path, spring means urging said actuator fromone limit of said lost motion connection and operative to move saidactuator relative to said driving member through said path to actuatesaid control member, and means to prevent movement of said actuator bysaid spring through said path, the last mentioned means operative torelease said actuator in response to predetermined movement of saidactuator by said driving member.

2. A control mechanism comprising a control member movable between twocontrol positions, means for moving said member from one of saidpositions to the other, a rotatable actuator including an arm movable ina rotary path in which it moves into and out of range of engagement withsaid control member during movement through a predetermined segment ofsaid path to engage and move said member from said other position towardthe rst mentioned position, power means including a rotating drivingmember having a lost motion driving connection with said actuatorpermitting rotation of said actuator relative to said driving member tocause movement of said arm through said segment of said pathindependently of said driving member, spring means urging said actuatorfrom one limit of said lost motion connection and operative to move saidactuator through said segment of said path to actuate said controlmember, and means to restrain movement of said actuator by said springthrough said segment of said path, the last mentioned means operative torelease said actuator in response to predetermined movement of saidactuator by said driving member.

3. A control mechanism comprising a control member movable between twocontrol positions, means for moving said member from one of saidpositions to the other, a rotatable actuator including an arm movable ina rotary path in which it moves into and out of range of engagement withsaid control member during movement through a predetermined segment ofsaid path to engage and move said member from said other position towardthe first mentioned position, power means including a rotating drivingmember having a lost motion driving connection with said actuatorpermitting rotation of said actuator relative to said driven member tomove said arm through said segment of said path independently of saiddriving member, spring means urging said actuator from one limit of saidlost motion connection and operative to move said actuator through saidsegment of said path to actuate said control member, means to restrainmovement of said actuator by said spring through said segment of saidpath, the last mentioned means operative to release said actuator inresponse to predetermined movement of said actuator by said drivingmember, and means forming a resilient operative connection between saidactuator and control member to permit movement of said arm through saidsegment of said path in the event the iirst mentioned means is operativeto urge said control member toward said other position.

4. A control mechanism comprising a control member movable between twocontrol positions, means for moving said member from one of saidpositions to the other, a rotatable actuator movable in a rotary path inwhich it moves into and out of range of engagement with said controlmember to engage and move said member from said other position towardthe first mentioned position, power means including a driving memberhaving a lost motion driving connection with said actuator permittingrotary movement between said driving member and actuator during movementof said actuator through said path, spring means urging said actuatorfrom one limit of said lost motion connection and operative to move saidactuator through said path to actuate said control member, and ayieldable detent engageable by a part of said actuator to restrainmovement of said actuator by said spring through said path, said detentbeing deected by movement of said actuator by said driving member andoperative to release said actuator at a predetermined angular positionof the latter.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 826,331 Harthan July 17, 1906 2,297,090 Weaver Sept. 29, 19422,366,635 McCloy Jan. 2, 1945 2,553,846 Clemens May 22, 1951

